Third and fourth generation mobile telecommunication systems, such as those based on the 3GPP defined UMTS and Long Term Evolution (LTE) architecture are able to support more sophisticated services than simple voice and messaging services offered by previous generations of mobile telecommunication systems.
For example, with the improved radio interface and enhanced data rates provided by LTE systems, a user is able to enjoy high data rate applications such as mobile video streaming and mobile video conferencing that would previously only have been available via a fixed line data connection. The demand to deploy third and fourth generation networks is therefore strong and the coverage area of these networks, i.e. geographic locations where access to the networks is possible, is expected to increase rapidly.
The anticipated widespread deployment of third and fourth generation networks has led to the parallel development of a class of devices and applications which, rather than taking advantage of the high data rates available, instead take advantage of the robust radio interface and increasing ubiquity of the coverage area. Examples include so-called machine type communication (MTC) applications, which are typified by semi-autonomous or autonomous wireless communication devices (i.e. MTC devices) communicating small amounts of data on a relatively infrequent basis. Examples include so-called smart meters which, for example, are located in a customer's house and periodically transmit information back to a central MTC server data relating to the customers consumption of a utility such as gas, water, electricity and so on.
Whilst it can be convenient for a terminal such as an MTC type terminal to take advantage of the wide coverage area provided by a third or fourth generation mobile telecommunication network there are at present disadvantages. Unlike a conventional third or fourth generation mobile terminal such as a smartphone, an MTC-type terminal is preferably relatively simple and inexpensive. The type of functions performed by the MTC-type terminal (e.g. collecting and reporting back data) do not require particularly complex processing to perform. As such, certain classes of telecommunications device, such as MTC devices, support “low capability” communication applications that are characterised, for instance, by the transmission of small amounts of data at relatively infrequent intervals. MTC devices are constructed so that individually they represent little burden on telecommunications networks and thus can be deployed in greater numbers than equivalent “full capability” terminals in the same networks.
In many scenarios, it is preferable to provide terminals dedicated to such “low capability” communication applications with a simple receiver unit (or transceiver unit) having capabilities more commensurate with the amount of data likely to be transmitted to (or from) the terminal.
To support MTC terminals, it has been proposed to introduce a “virtual carrier” operating within a bandwidth of one or more “host carriers”: the proposed virtual carrier concept preferably integrates within the communications resources of conventional OFDM based radio access technologies and subdivides frequency spectrum in a similar manner to OFDM. Unlike data transmitted on a conventional OFDM type downlink carrier, data transmitted on the virtual carrier can be received and decoded without needing to process the full bandwidth of the downlink OFDM host carrier. Accordingly, data transmitted on the virtual carrier can be received and decoded using a reduced complexity receiver unit: with concomitant benefits such as increased simplicity, increased reliability, reduced form-factor and lower manufacturing cost.
However, when operating alongside each other the differing capabilities of conventional LTE devices and MTC devices may lead to increased complexity resource allocation and scheduling. Consequently, efficient operation of a wireless telecommunications system for MTC devices and conventional and legacy LTE devices is therefore desirable.
Other examples of “low capability” devices include those devices with a smaller number of receiving antennas than devices of “full capability” terminals and those devices with an ability to process a smaller number of information bits in a given time span than “full capability terminals”.
Typically, “full capability” and “low capability” may be determined by reference to the specifications of a telecommunications network, and the specifications may make relative capability explicitly or implicitly stated.